An American emergency room doctor said the chances of living through a fall from that height are about 1 in 100.

The man, identified by the New Zealand Herald as Tom Stilwell, a British man in Auckland on a "working holiday," returned home after a night out with friends and found he did not have a key to get into his locked apartment. Stilwell tried to jump down to his balcony from the balcony of the apartment above, but instead plummeted to the roof of a building below.

Stilwell's story astounded his doctors in New Zealand as well as in the United States.

"It made me wonder what the roof looked like that he fell on," said Dr. Nicholas Kman, associate professor of emergency medicine at The Ohio State University Medical Center.

"It's pretty abnormal for someone to fall that far and survive," Kman said. "For every fall like that, the odds of living are very rare."

Doctors use a formula called "lethal doses" to determine the likelihood of death in a fall. At four stories, or about 48 feet above the ground, half will survive. But at seven stories or 84 feet, only 10 percent are expected to live -- that is, 90 percent will die, according to Kman.

According to local reports, Stilwell fell 13 stories. At first, he was in critical condition at Auckland City Hospital, but was later upgraded to satisfactory with neck and back fractures, a broken wrist and suspected internal injuries.

ABCNews.com reached out to the hospital, but its public affairs office was closed because of the time zone difference.

Stilwell's upstairs neighbor, Geraldine Bautista, 28, told the Herald that he knocked on her door on the 15th floor of the Volt Apartment building at about 2 a.m., asking if he could jump off her balcony onto his to get into his own apartment.

According to the Herald, he went straight to the balcony and Bautista grabbed his hand, but he fell.

"It happened so fast," she told the newspaper. "It happened within seconds. I couldn't even scream for help. He was like a paper falling from here."

Friends said that Stilwell had "a fair bit to drink" before the incident, according to the Herald.

Doctors say that although there is no evidence that alcohol softens the blow to the body, they have heard that anecdotally about car accident victims.

"There is no science behind that," Kman said. "Most doctors are reluctant to say it happens. But in my experience in trauma, it does seem to be something that happens. But that is not likely from a fall."

A person's age, the height of the fall, the nature of the surface hit and the body part that first touches the ground are all factors in the severity of the injuries and the prognosis for recovery.

"If you fall out of a tree and hit a bunch of branches, it may slow the fall," he said. "Landing on grass is better than cement."

Head injuries have the lowest survival rate, according to Kman.

Other dangerous injuries occur when a person lands feet first.

"The heel hits and transmits the force up the back," he said. "When someone jumps off a parking garage or building they break their heel bones and then the lower spine. When they break the feet, we always X-ray the back, because that's a common injury."

Sometimes, paralysis can occur if there is a spinal cord injury.

Emergency room doctors see most fall victims during the summer months, and they are usually window cleaners working on scaffolding and roofers.

Falls are most common among the elderly, the second cause of unintended death for trauma behind motor vehicle accidents, according to Kman.

The reason, say veterinary researchers is that cats have a larger surface area for their weight as they fall with legs extended, which gives them a lower terminal velocity -- about 60 mph, compared to an average-sized male at about 120 mph. When cats hit the ground, they have fewer injuries.

In physics, terminal velocity is the constant speed attained by a body while falling through a gas or liquid.

"Terminal velocity is something that plays into this," Kman said. "But people are not meant to fall off three-story buildings. And I have a feeling that you reach [terminal velocity] some point before 15 floors."